Devices for converting radiant energy, such as optical energy, into electric energy presently generally take two forms; viz: (1) semiconductors relying upon a barrier layer mechanism, and (2) pyroelectric devices wherein a ferroelectric is cyclically heated and cooled to provide corresponding changes in the capacitance and resistance of a capacitor including the ferroelectric.
Typically, the barrier layer semiconductor devices have relatively heavily doped semiconductor layers. These devices are utilized as radiant, optical energy detectors for specific wavelengths of interest, as well as power generating solar cells. The major disadvantage of the semiconductor devices as radiant energy detectors is that the semiconductor element must be maintained at cryogenic temperatures to function effectively. It is frequently difficult to maintain a semiconductor device at a cryogenic temperature, whereby the usefulness of semiconductor radiant energy detectors is frequently limited. The major disadvantage of the semiconductor devices as solar energy converters in that such devices are relatively inefficient in converting the solar energy into electrical energy. The typical, actual maximum efficiency of such converters is generally on the order of 10%.
Pyroelectric devices are generally characterized by a ferroelectric dielectric that is positioned between a pair of electrodes to form a capacitor responsive to the optical energy. Typically, the ferroelectric material is periodically heated and cooled to cause a periodic variation in the capacitance and resistance of the capacitor. Since the ferroelectric materials have dipole layers extending completely through the dielectric, i.e., from one electrode to the other electrode, the dielectrics are strongly piezoelectric, making them sensitive to vibrations. I know of no prior art device using a pyroelectric device to convert radiant energy to electric energy. This is because all of the prior pyroelectric devices of which I have knowledge have a relatively low, approximately unity gain factor. The gain factor is determined by the ratio of activation energy for the variation of the capacitance of the material to the temperature of the material, and for a given amplitude of the temperature variation of the material, the larger the gain factor the higher the efficiency of the device in converting thermal energy to electric energy.